Basic LAN QoS (Cisco) and VLANs in a Single Switch Network

When deploying IP telephones, Genesys recommends that you place IP telephones in a voice virtual local area network (VLAN). A voice VLAN can protect the telephones from broadcast traffic and provide security. Place all voice endpoints, including the Interaction Media Servers and other servers in the CIC network environment, in the voice VLAN. CIC clients should remain in a Data VLAN or the Default VLAN. You can also place the SIP Soft Phone on the Default VLAN. Splitting traffic requires dual Network Interface Cards (NICs). This configuration is only possible on switches that support Layer 3 routing. To allow the different networks communicate with each other requires Layer 3 routing. You configure it in the routing table on the switch.

This example configuration is based on the recommended setup and the following network model using a Cisco Catalyst 3560 switch.

1. Create the VLAN for Voice.

   Start in the privileged exec mode:

         configure terminal
         vlan 200
         name "Voice"
         exit
         

2. Configure the VLAN interfaces with IP addresses.

   From the global configuration mode:

         interface vlan 100
         ip address 10.70.0.1 255.255.0.0
         interface vlan 200
         ip address 10.60.0.1 255.255.0.0
         

3. Assign the switch ports to the respective VLANs using static port assignment.

   From the global configuration mode:

         interface range FastEthernet 0/1-12
         switchport access vlan 200
         exit
         

4. If using CDP (alternative to step 3)

   Some environments may only have one data drop to the user. In this case, it is possible to use the PC port on the back of most of the Polycom telephone models.

   The Polycom telephones support CDP to configure the correct VLANs for voice and data. The client personal computer can be plugged into the PC port of the Polycom telephone and still appear on VLAN 100 while the voice traffic from the telephone appears on VLAN 200.

   Other endpoints that do not support CDP need static VLAN assignments on the switch. In the following example, ports 1 to 4 assign statically, and ports 5 to 12 assign using CDP.

   From the global configuration mode:

         interface range FastEthernet 0/1-4
         switchport access vlan 200
         mls qos trust dscp
         interface range FastEthernet 0/5-12
         mls qos trust dscp
         switchport voice vlan 200
         exit
         

5. Enable Layer 3 routing between the VLANs on the switch.

   From the global configuration mode:

         router rip
         version 2
         network 10.0.0.0
         ip routing
         ip route 10.60.0.0 255.255.0.0 Vlan200
         ip route 10.70.0.0 255.255.0.0 Vlan100
         ip route 0.0.0.0 0.0.0.0 Vlan100 10.0.0.1 
    
    
    //default route
         

6. Enable DHCP relay on the voice VLAN 200.

   By design, DHCP broadcasts don't forward across VLANs. The following configuration enables the relay of DHCP broadcasts from VLAN 100 to VLAN 200. This example assumes the DHCP server resides on the default VLAN 100 and has an IP address of 10.70.0.5

   From the global configuration mode:

         interface vlan 200
         ip helper-address 10.70.0.5
         exit